I’d take it at face value, 25K tons of shipyard. Whatever building capacity that is would be secondary in this instance.
Which implies that shipyards under 25K tons can’t build or repair jump drives. Which seems weird.
Yes to #1 : It says shipyard, not build capacity, has to be 25Kt, so build capacity might only be 12.5Kt (or less, if Starship Workers Local 404 are on strike or out with the flu, blue or otherwise).
Not necessarily to #2: The system needs a Class A starport to build starships, but the shipyard need not be the starport (or all of it) - it comes back to that whole "
Is one starport equal to one facility?" discussion. The requirement is the extra cost per ton (MCr 0.75), the Tech Level required for the drive (TL9 for J1, TL11 for J2, etc.) and I would add, though it doesn't say so, that the system in its UWP should be rated as having a Class A starport, which might or might not include that particular shipyard.
But, the station in and of itself cannot be
that starport on its own, unless it has 25kt of shipyard space as part of the station.